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to act as nucleation sites. The heats with RE silicide ad- ditions had the higher TRE levels in Figure 6. The likely cause of this higher recovery is the higher silicon content of the ferroalloy protecting the RE from oxidation prior to entering the steel.


dercooling in the alloy, which enables the La2 O3


There were several RE containing samples with yield strengths higher than the baseline as-cast 1030 heat (See Figure 7). The average yield strength for the baseline heat was 262 MPa. The average strength for the 1030 with 0.2% misch metal was 319 MPa. It is interesting to note that the 1030 with 0.2% RE silicide sample had a similar average yield strength and UTS to the baseline despite a significantly lower carbon level. Unlike the 1010 results, the UTS was


particles


lower for several samples. Two-thirds of the samples with low UTS contained a La2


for the tensile bars showed no indication of a significant dif- ference (See Figure 8).


O3


Evaluating the strength as a function of TRE reveals behav- ior different from 1010 steel (Figure 9). Yield strength in- creased with the TRE content. The 1030 samples containing 0.099% TRE with 0.2% rare earth silicide had dramatically lower carbon content than the other samples. The lower car- bon content would explain their significantly lower strength.


Optical Microscopy


Representative micrographs of the 1010 samples without La2


O3 powder addition are illustrated in Figures 10-14.


powder addition. The elongation


Figure 6. Yield strength verses the actual rare earth content of each 1010 tensile bar tested.


Figure 8. Percent elongation of the 1030 samples.


Figure 7. Yield strength and ultimate tensile strength for 1030 samples.


56


Figure 9. Yield strength as a function of TRE for the 1030 samples.


International Journal of Metalcasting/Spring 2012


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